1074 



HUMAN ANATOMY. 



as a large irregularly crescentic tract of transversely cut fibres that occupies the 

 greater part of the periphery. ( 2 ) The descending root of the vestibular nerve is seen 

 to the inner side of the dorso-mesial border of the restiform body as a field of loosely 

 grouped bundles of cross-sectioned nerve-fibres. (3) The fasciculus solitarius, or 



Fasciculus solitarius 



FIG. 928. 



Dorsal nucleus of X 

 , Nucleus of XII 



I Post. long. 



\ fasciculus 



Ventricular roof 





Nucleus ambiguus 

 Root-fibres of 



>Restiform body 



Descending 

 vestibular root 



Gray column 

 of vestibular root 

 Form.retic.grisea 

 Form, retic. alba 

 Interolivary stratum 

 median fillet) 



Inferior olivary nucleus 



Pyramidal tracts ^"Tir-v '^JSJjj&iSs 



Transverse section of medulla at level F, Fig. 919; ventricular floor is wide; restiform body well established ; 

 descending root of vestibular nerve is seen. X 5. Preparation r>y Professor Spiller. 



descending root of the vagus and glosso-pharyngeal nerves, shows as a conspicuous 

 transversely cut bundle which lies ventro-mesially to the vestibular root. (4) The 

 descending root of the trigeminal nerve is easily identified as a superficial crescentic 

 field that on its mesial aspect encloses the remains of the substantia gelatinosa Rolandi. 

 The lateral area, between the diverging vagus and hypoglossal root-fibres, is 

 chiefly occupied, in addition to (i) the inferior olivary and (2) dorsal accessory 

 olivary nucleus, by the feltwork of fibres producing the reticular formation. In con- 

 trast to that within the 



FIG. 929. anterior area, the retic- 



ulum within the lateral 

 area contains a con- 

 siderable amount of 

 diffuse gray matter be- 

 tween its fibres, and, 

 hence, is known as (3) 

 the formatio rcticularis 

 grisca. Accessions to 

 the irregularly distrib- 

 uted nerve-cells occur 

 as two moredefinitecol- 

 lections ; one of these, 

 (4) the nucleus aw- 

 biguns. consists of an 

 inconspicuous group of 

 laroe cells lying about 

 the middle of the gray 

 reticular substance and is of importance as the nucleus of origin of at least part of 

 the motor fibres of the vagus nerve. The other (5 ), the nucleus latrra/is, includes 

 an uncertain aggregation of medium sized cells, situated near the periphery and ventral 













Nerve-cell 



Transverse 

 fibres 



Longitudinal _ *?fyf <,* 



fibres 



\ ' ' 



. "''"-. 



"**" -~ 



Portion of formatio reticularis gris:i. showing nerve-cells and interlacing 

 tt;msverse and longitudinal fibres. X 13- 



